NCP1501

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7

Voltage Output Selection

The output voltage selection is accomplished via two

external pins: CB0 and CB1. If CB0 and CB1 pins are left

floating by the external circuit, the output voltage will

default to 1.35 V. The corresponding voltages are as follows.

NCP1501

CB0

CB1

0

0

1.05

0

1

1.35

1

1

1.57

1

0

1.80

Figure 6. Transition Waveforms from

LDO to PWM Mode

0

3.0

0

010

External SYNC Signal

Internal CLK Signal

TIME

(m)

1.35 V

Figure 7. Power Up and Power Down Sequence

1.8 V

1.05 V

1.57 V

SHD

CB0

CB1

Thermal Shutdown

Internal Thermal Shutdown circuitry is provided to

protect the integrated circuit in the event that the maximum

junction temperature is exceeded. When activated, typically

at 160

°C, the PWM latch is reset and the linear regulator

control circuitry is disabled. The thermal shutdown circuit

is designed with 25

°C of hysteresis. This means that the

PWM latch and the regulator control circuitry cannot be

re−enabled until the die temperature drops by this amount.

This feature is provided to prevent catastrophic failures from

accidental device overheating. It is not intended as a

substitute for proper heatsinking. The NCP1501 is

contained in the Micro−8 package.